Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field.
With the development of more complex optical networks, the capabilities of optical switching devices are evolving. Switches, such as wavelength selective switches (WSS) are incorporating more input and output ports to manage the increased system demand. Further, WSS devices can be configured to independently route signals from two sources within a single device. In such a configuration, a single WSS device essentially operates as two separate devices. An example of a dual source or “twin” device is described in U.S. Pat. No. 7,397,980 to Frisken, entitled “Dual-source optical wavelength processor” and assigned to Finisar Corporation.
However, constraints on the size of the device generally place limits on the number and location of possible ports and the functionality of the device. Further, with increased port numbers, directivity issues become more prominent as the number of possible switching states gives rise to undesired connectivity between pairs of ports. That is, establishing a particular link between two ports simultaneously establishes links between other pairs of ports. Such undesired links become more common as the number of ports in a switching device increases and also as the number of network switching points increases, particularly in networks utilizing bidirectional dual source WSS devices. Undesired links between ports can establish or enhance multipath interference in the beam along the path and can also cause instability in source transmitters such as lasers.
In the case of dual source devices, the independent routing of a dual source device can be difficult to maintain as the setting up of switching states of a first optical source may simultaneously couple signals to ports intended for the second source. In both single source and dual source devices, this connectivity issue is often addressed by setting up of isolator arrays on the input ports. However, this adds to optical loss, size and cost.
There is a need for improved port isolation in optical switching devices.
In current dual source WSS devices beams from the two sources are propagated separately in space through the optical system. This separation of beams requires larger sized optical components and gives rise to increased physical device size compared to conventional single source devices. Increase component and device size typically leads to increase manufacturing cost.
There is also a need for improved dual source WSS devices.